Illustration of the spike protein (red) from the B.1.531 variant of the SARS-CoV-2 coronavirus, the cause of the respiratory illness Covid-19. The mutation site of the new variant is yellow. The spike protein binds to angiotensin converting enzyme 2 (ACE2, blue) in the host cell membrane, mediating viral entry to the host cell. B.1.531 was first identified in the South Africa. Its mutation may help it evade the immune system.